Do not skip ERROR:/SUCCESS: response from management interface

Do not skip ERROR:/SUCCESS: response from management interface

Generally we expect a response of SUCCESS: or ERROR: to every
command sent to the management interface. But, while in
the management-hold state, sending "signal foo" returns only
the following reply (with foo = SIGHUP, SIGUSR1 etc.):

>HOLD:Waiting for hold release:0

Fix by always responding

ERROR: signal 'foo' is currently ignored"
followed by the above line.

Though this is seldom seen in practice[*], such violation of the
protocol could stall clients like the GUI. So fix it.

[*] One way this happens is with SIGHUP sent before the daemon
is on hold state which it enters before the SIGHUP is received.

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20220728034508.15180-1-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24750.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 579b78e22feab7fe7cc627355cbb270cd91aebb4)